عنوان مقاله [English]
Background and objectives: The accurate information about the spatial distribution of land suitability assessment are important elements for sustainable land management and diversity is a way for measuring soil variation. Beside, soil surveys are important sources of data that can be used to improve land suitability classifications. Unfortunately, comparing the variation of land suitability using diversity indices and different soil mapping approaches is rarely considered. Therefore, the main objective of this study was to investigate the viewpoint of different soil mapping approaches (conventional and digital soil mapping) for description the variation of suitability class and subclass for main irrigated crops (wheat, maize, alfalfa and potato) in Shahrekord plain of Chaharmahal-Va-Bakhtiari province.
Materials and methods: The area under investigation has a size of approximately 10000 ha. 120 pedons with approximate distance of 750 m were excavated and described. Soil samples were taken and their physicochemical properties were determined. Soil map was prepared at family level. For the representative pedons, the average of soil properties was determined by considering the depth weighted coefficient up to 100 and 150 centimeters for annual and perennial crops, respectively. Based on FAO framework, suitability class and subclass for main irrigated crops were determined using parametric method. Also, Random Forest model was used to predict suitability class and subclass for all of the crops. Then, for each crop, the map units that have the highest frequency in land suitability conventional map were selected as indicator to calculate functional diversity indices. The selected map units were overlaid on digital maps and diversity indices were calculated. Then, the mean of Shannon’s diversity index for two approaches was statistically evaluated.
Results: For all of the studied crops, significant difference was not observed for diversity between mean values of conventional and digital maps at class level. However, in the subclass level, a significant difference (95% confidence level) was obtained only for potato. For all of the studied crops, regardless the mapping approaches, diversity indices showed higher values in the subclass level than class level of suitability. This difference was significant at 0.001 probability level for alfalfa, maize and potato using two mapping approaches and for wheat in digital maps.
Conclusion: No significant difference was observed between two mapping approaches for all of the studied crops confirm that description the variation of suitability class and subclass less influenced by the land use type and mapping approaches. The results recommended that revision of the FAO criteria to include the spatial distribution of soil properties for sustainable land management.